Photographic dye diffusion transfer process using silver salt transfer for reversal

ABSTRACT

In a color photographic material positive color images are produced by the dye diffusion transfer process. The reversal is brought about by the silver salt diffusion process. The lightsensitive element contains up to three separate color units each unit comprising a light-sensitive silver halide emulsion layer and an associated nuclear layer containing development nuclei and a non-diffusible dye-giving compound capable of releasing a diffusible dye after on oxidative condensation with developer compound. The light-sensitive silver halide emulsion contains a non-diffusible silver halide developer. The nuclear layer contains a non-diffusible developer compound capable of being oxidatively condensed with the dye-giving compound to release the diffusible dye. Development is carried out in the presence of catalytic amounts of a diffusible auxiliary developer. The imagewise distribution of liberated diffusible dye is transferred to an image receptor layer.

United States Patent Wingender et al.

1 PHOTOGRAPHIC DYE DIFFUSION TRANSFER PROCESS USING SILVER SALT TRANSFER FOR REVERSAL [75] Inventors: Kaspar Wingender, Leverkusen;

Hans Vetter, Cologne, both of Germany [73] Assignee: Agfa-Gevaert Aktiengesellschaft,

Leverkusen-Bayerwerk, Germany [22] Filed: May 28, 1974 [21] Appl. No.: 473,790

[30] Foreign Application Priority Data June 1, 1973 Germany 2327963 [52] US. Cl. 96/3; 96/29 D; 96/77 [51] Int. Cl. 603C 7/00; GO3C 5/54; 003C 1/40 [58] Field of Search 96/129 D, 77

[56] References Cited UNITED STATES PATENTS 3,443,940 5/1969 Bloom et al. 96/3 3,628,952 12/1971 Puschel et al 96/29 D Dec. 9, 1975 [57) ABSTRACT In a color photographic material positive color images are produced by the dye diffusion transfer process. The reversal is brought about by the silver salt diffusion process. The light-sensitive element contains up to three separate color units each unit comprising a light-sensitive silver halide emulsion layer and an associated nuclear layer containing development nuclei and a non-diffusible dye-giving compound capable of releasing a diffusible dye after on oxidative condensation with developer compound. The light-sensitive silver halide emulsion contains a non-diffusible silver halide developerv The nuclear layer contains a nondiffusible developer compound capable of being oxidatively condensed with the dye-giving compound to release the diffusible dye. Development is carried out in the presence of catalytic amounts of a difiusible auxiliary developer. The imagewise distribution of liberated diffusible dye is transferred to an image receptor layer.

7 Claims, 1 Drawing Figure U.S. Patent Dec. 9, 1975 3,925,075

FIG. I

PHOTOGRAPIIIC DYE DIFFUSION TRANSFER PROCESS USING SILVER SALT TRANSFER FOR REVERSAL This invention relates to a photographic dye diffusion transfer process for the production of positive colored transfer images using a photographic material and more particularly a monosheet material which comprises at least one light-sensitive silver halide emulsion layer and at least one non-diffusible dye-giving compound, photographic reversal being carried out by the silver salt diffusion process.

Monosheet materials for producing colored transfer images are already known. They may, for example, comprise the following layer elements:

a transparent support layer A,

an image receiving layer B,

a light-sensitive element C containing at least one light-sensitive silver halide emulsion layer and at least one non-diffusible dye-giving compound and a cover sheet D as well as at least one container arranged at the side which can be split open and contains a processing liquid provided for the development of the exposed lightsensitive layer, which container, when acted upon by mechanical forces, releases its contents between two adjacent layer elements of the monosheet material.

The finished image produced in the image receiving layer B in all cases becomes visible through the transparent support layer A. In order to show it up against the light sensitive element C in which the developed silver and in some cases residues of dye remain, and in order to obtain an attractive background for the image, a lightreflecting layer is provided between the image receiving layer B and the light-sensitive element C. This reflecting layer may have been present initially or it may be produced during development, for example by pressing a liquid which contains a light reflecting substance between the layer elements B and C. The second method would be used if, for example, the cover sheet D were not transparent. In that case, the exposure of the light-sensitive element and the viewing of the finished images must both be carried out from the same side. A side reversed image appears. To produce images which are non-side-reversed, it is necessary to use optical reversal systems (mirrors). These can be omitted if exposure of the light-sensitive element and view ing of the transfer image produced in the image receiving layer are to be carried out from different sides. In that case, however, the cover sheet D must be transparent and a light-reflective layer may initially be present between the layer elements B and C.

Compounds from various classes have been proposed as non-diffusible dye-giving compounds for the dye diffusion transfer process. Dye-giving compounds of this kind have been described, for example in German Patent No. l,O95,ll5; German Offenlegungschrift No. 1,772,929; 1,930,215 and 2,242,762.

A common feature of all these dye-giving compounds is that they are non-diffusible dye-giving compounds which are capable of liberating difi'usible dyes as a result of a reaction with developer oxidation products. Another common feature of these dye-giving compounds is that they are negatively operating systems. To produce positive colored transfer images, it is therefore necessary to use a photographic reversal process if the usual negative emulsions are employed. The silver salt diffusion process constitutes such a reversal process. Photographic reversal by means of the silver salt diffusion process to produce positive color images using conventional color couplers has been described, for example, in U.S. Pat. No. 2,673,800. A light-sensitive element which is suitable for the dye diffusion transfer process is obtained by replacing the color coupler by the above mentioned dye-giving compounds. A light-sensitive element of this kind may comprise, for example at least one combination of a light-sensitive silver halide emulsion layer and, associated with this layer, a layer of binder which contains development nuclei for physical development and a dye-giving compound.

In the development process, the exposed portion of silver halide in the light sensitive silver halide emulsion layer is chemically developed. The unexposed portion is transferred by means of a silver halide solvent to the associated binder layer which contains development nuclei, and is physically developed there. lf the developer used for physical development is one which, in its oxidized form, is capable of liberating a diffusible dye as a result of a reaction with the dye-giving compound present in this layer, then diffusible dyes are obtained in image distribution and can be transferred to an image receiving layer where they form a positive color image. To ensure that the developer oxidation product formed by chemical development in the light-sensitive silver halide layer does not also contribute to the formation of diffusible dyes, which would result in an increased color fog, separating layers are normally arranged between the light-sensitive silver halide emulsion layer and the associated binder layer which contains the development nuclei. These separating layers contain compounds which can react irreversibly with developer oxidation products. for example non-diffusible color couplers or non-diffusible hydroquinone derivatives. At least three layers are therefore necessary for each color unit. Furthermore, additional separating layers are required between the individual color units in order to prevent accidental diffusion of soluble silver salt complexes. The whole photographic material therefore has a highly complicated structure which in the case of three color units comprises at least eleven layers in the light sensitive element alone.

It was found that the image whites of colored transfer images obtained with such a material are not completely satisfactory even if the above mentioned separating layers are provided. The images tend to turn yellow or brown after some time, particularly in the light areas. This effect appears particularly seriously with monosheet materials which are maintained as integral unit even after processing.

It has now been found that the disadvantages mentioned above can be reduced or substantially obviated by using non-diffusible developer substances which are incorporated in the layers and by developing with an alkaline activator solution in the presence of catalytic quantities of a diffusible auxiliary developer. Furthermore, the above mentioned separating layers situated within the color units can be omitted without the result being thereby deleteriously affected. This method of development requires, of course, the use of dye-giving compounds which already contain a preformed dye in their molecule or a dye precursor which can be transformed into a dye without reacting it with developer oxidation products because a dye which would first have to be produced by oxidative coupling of a dye-giving compound with non-diffusible developer present in the same layer would inevitably be non-diffusible, and thus would be useless for the process of the invention.

This invention relates to a photographic dye diffusion transfer process for producing positive colored transfer images in which a negative silver image is produced by development in at least one light-sensitive silver halide emulsion layer of a photographic material which has been exposed imagewise, and the silver halide which remains undeveloped is transferred by means ofa silver halide solvent into an associated layer of binder which contains development nuclei where it is developed to a positive silver image and, at the same time, developer oxidation products are produced, whereupon a preformed, diffusible dye is liberated imagewise from a noxdiffusible dye-giving compound in this associated layer as a result of a reaction with the developer oxidation products produced in this layer, and the diffusible dye liberated is transferred to an image receiving layer, characterised in that the lightsensitive silver halide emulsion layer contains a non-diffusible silver halide developer compound which is not capable of an oxidative condensation reaction with the non-diffusible, dyegiving compound, and that the associated layer of binder which contains development nuclei contains a non-diffusible developer compound which, in its oxidized form, is capable of liberating the preformed dye from the dye-giving compound as a result of a condensation reaction with this compound, and that development is carried out in the presence of catalytic quantities of a diffusible auxiliary developer,

Any developer compounds may be used as non-diffusible silver halide developer compounds provided that they are capable of developing silver halide sufficiently rapidly and are sufficiently diffusion resistant in the light-sensitive silver halide emulsion layer. In prin ciple, non-diffusing developers from all classes of developers may be suitable, e.g. non-diffusible derivatives of 0- or p-dihydroxy-benzene, p-aminophenol, or ascorbic acid but particular care should be taken to ensure that the selected developer will bring about rapid development of the exposed silver halide. This chemical development should proceed so rapidly that it is substantially complete before undeveloped silver halide is converted into a silver complex compound, transferred to the associated binder layer which contains development nuclei and physically developed there because, a high color fog would otherwise be formed in the light parts of the image and color separation would be unsatisfactory. Non-diffusible derivatives of hydroquinone have therefore provided to be particularly suitable for this purpose, especially those of the following formula wherein R represents a linear or branched chain alkyl group preferably containing from 8 to 20 carbon atoms, R represents hydrogen, an SO H group or a linear or branched chain alkyl group preferably containing 8 to 20 carbon atoms and R and R together contain at least 12 carbon atoms.

the non-diffusible developer compound in the associated layer or binder which contains nuclei for physical development should, in their oxidized form, react with the dye-giving compound to liberate a preformed, diffusible dye from them.

From the dye-giving compounds of US. Pat. No. 3,628,952 and those dye-giving compounds of US. Pat, No. 3,227,550 which contain a preformed dye portion and those dye-giving compounds of US. Patv No. 3,443,940 which are capable of oxidative coupling, the non-diffusible developers used according to this invention are capable of ente ring into an oxidative condensation reaction with the dye-giving compounds of split off a preformed diffusible dye. Developers of this kind include. in general, all color-forming developer compounds based on p-phenylenediamine which contain a primary amino group, for example those described in US. Pat. No. 3,705,035 and, in some cases, for example, also derivatives of l ,Z-dihydroxybenzene which are free from substituents at least in one para-position to a hydroxyl group.

Both types of developer compounds those incorporated in the light-sensitive silver halide emulsion layers and those incorporated in the binder layers which are associated with the said silver halide emulsion layers and which contain development nuclei should be nondiffusible in the layers. For this reason they are provided with chemical groups which confer diffusion resistance, These groups are preferably organic groups which may in general contain straight or branched chain aliphatic groups and may also contain carbocyclic or heterocyclic arom atic groups. The aliphatic portion of these groups generally contain from 8 to 20 car bon atoms. These groups are connected to the remainder of the molecule either directly or indirectly, e.g. through one of the following groups: CONH, SO NH, CO, -SO O-, S or NR where R denotes hydrogen or alkyl. Compounds which, by virtue of their constitution, still have a certain hydrophilic character or can be incorporated hydrophilically in the layer by suitable additives in spite of being diffusion fast within a binder are particularly suitable. Thus, for example it is advantageous to disperse noctadecylhydroquinone hydrophilically in gelatine by using it as a mixture with n-octadecyl-hydroquinone sulfonic acid. In the process according to this invention, development is carried out using an alkaline development liquid in the presence of a diffusible auxiliary developer compound. This auxiliary compound may be present in the developer liquid or it may advantageously be accommodated in one or more layers of the light-sensitive element. The auxiliary developer is advantageously used only in catalytic quantities, that is to say in quantities which, in the absence of other developer compounds in the photographic material, are quite insufficient to effect chemical development of the silver halide in the light sensitive layer or physical de velopment after transfer to the associated layer of binder which contains development nuclei. The quantity of auxiliary developer used is preferably between 0.02 and 0.2 mol per mol of silver halide. The auxiliary developer must, in all cases, be capable of the reversible transfer of electrons. The following are examples of suitable auxiliary developerszp-Methylaminophenol; 2.4-diaminophenol; p-benzylaminphenol;l-phenylilpyrazolidone and reductone.

If the diffusible auxiliary developer is used in the catalytic quantities indicated above, itco-operates advantageously with the non-diffusible developer in the silver halige emulsion layer, Both the auxiliary developer which is present in catalytic quantities and the non-dif fusible developer which is present in stoichiometric quantities that means in quantities which are comparable to the amount of silver halide or to the amount of dye-giving compound are unable, separately, to develop the silver halide rapidly and sufficiently completely. Rapid and complete development becomes possible only by the combination of the two developers. If the quantity of diffusible auxiliary developer present is too small, chemical development proceeds too slowly even if non-diffusible developer is present. The transfer of complex silver halide to the adjacent nuclear layer sets in too early. Physical development in this layer is also then insufficiently strong. The transfer image has neither satisfactory whites nor high color densities. If the quantity of diffusible auxiliary developers is too high, the fog developed in the silver halide emulsion layer is too high. Insufficient silver halide is then available for physical development in the dye-giving layer. Although satisfactory whites are obtained, only weak color densities are obtained in the transfer image.

Colored transfer images with substantiallyimpmv-ed image whites are obtained by the process according to the invention. In addition, the use of non-diffusible developer in the layers of light sensitive element makes it possible to dispense with separating layers in the given color unit as well as with the separating layer which may otherwise be provided between the light-sensitive element and the image receiving layer for the purpose of intercepting developers in the oxidized and non-oxidized form and, consequently, the arrangement of layers as a whole is considerably simplified. If the separating layers in the color units are omitted, it is particularly advantageous according to this invention if the non-diffusible developer used in the light-sensitive silver halide emulsion layer is always functionally distinct from the developer in the associated layer of binder which contains development nuclei, in that the oxidized form of the first mentioned developer should not be capable of undergoing a condensation reaction with the dye-giving compound. In this embodiment of the process, the dye-giving compound present in the layer of binder which contains development nuclei and the non-diffusible developer also present in this layer are capable of undergoing an oxidative condensation reaction with each other to liberate a diffusible preformed dye. The non-diffusible silver halide developer present in the light-sensitive silver halide emulsion layer, on the other hand, is not capable of reacting in the same way with the dye-giving compound. This means that the dye-giving compounds must be specially selected and only those non-diffusible dye-giving compounds are capable of liberating the diffusible dyes only when an oxidative condensation reaction takes pleace with the developers and not simply as a result of the transfer of electrons. Suitable dye-giving compounds for this purpose are in particular those described in US. Pat. No. 3,628,952 and also, for example, those among the compounds described in US. Pat. No. 3,227,550 which already contain a preformed dye radical and those among the compounds described in US. Pat. No. 3,443,940 which are capable of a coupling reaction with color-forming developer oxidation products in the ortho position to the sulfonamide group. In the case of the last two mentioned classes of dye-giving compounds, the choice of non-diffusible developers is restricted to those based on p-phenylene diamine which contain a primary amino group whereas, in the case of the first mentioned dye-giving compounds, non-diffusion pyrocatechol derivatives may also be used as developers.

According to the invention, the developers in the silver halide emulsion layer are not capable of reacting in the oxidized form with the dye-giving compound to liberate the diffusible dye. The following are examples of such developers:

l on

OH @Hfn a c l on 1/ I s 17 (n)ll C (CPQSO3H 16 55 11/11 H2N--N (CHZMSOBH (CHZMSOBH According to this invention, therefore, the lightsensitive element of the photographic material, particularly of the monosheet material comprises in the simplest case, a light-sensitive silver halide emulsion layer and, associated with this layer, a layer of binder which contains nuclei for physical development. The silver halide emulsion layer contains a non-diffusible black-andwhite developer. The nuclear layer contains a non-diffusible dye-giving compound with a preformed dye group and a non-diffusible developer substance which, in its oxidized form, is capable of entering into a condensation reaction with the dye-giving compound to liberate a diffusible dye. In the case of a photographic material for the production of multicolored transfer images, the light-sensitive element contains three color units for the colors yellow, magenta and cyan. The prevailing sensitivity range of the light-sensitive silver halide emulsion corresponds in each case to the spectral absorption range of the image dye liberated from the associated dye-giving compound. This means that the blue sensitive silver halide emulsion layer has associated with it, a dye-giving compound which forms a yellow dye, the green sensitive silver halide emulsion layer has associated with it a dye-giving compound which forms a magenta dye and lastly, the red sensitive silver halide emulsion layer has associated with it a dye-giving compound which forms a cyan dye.

The process according to the invention has the following advantages: The separating layers within the color units between a light-sensitive silver halide emulsion layer and the associated nuclear layer are dispensed with. This results in a simplification of the composition of layers and moreover, the diffusion paths for the dissolved silver halide and for the liberated dyes are substantially shortened. This again provides the necessary condition for rapid development and for obtaining high color densities. Since the major portion of developer substances is displaced into the layers, the problem of depletion of developer is overcome, especially in those layers most remote from the place where the developing liquid is released. A simple alkaline activator paste which is completely resistant to oxidation may be used. The amount of organic substances in the activator liquid is reduced and consequently the thickness of the activator layers can also be substantially reduced. Lastly, the problem of barrier layers for unused devel oper does not arise.

The developer paste consists mainly of alkali. a binder which increases the viscosity, a silver halide solvent such as thiosulfate and, preferably, also an auxiliary developer. If desired, however, the thiosulfatc and auxiliary developer may be incorporated in the structure of layer. To develop the photographic material, the exposed portion of silver halide is chemically devel oped by the incorporated developer with the aid of auxiliary developer while the unexposed portion of silver halide is dissolved by thiosulfate and physically developed in the associated color producing nuclear layer by the developer incorporated therein, with the aid of auxiliary developer. The developer oxidation product reacts with the dye-giving compound and diffusible cyan. magenta and yellow dyes are formed in imagwise distribution and migrate into the image receiving element where they form a positive copy of the original. It is even advantageous if only the light-sensitive silver halide layer contains a diffusion-fast developer. In this case, each color unit again comprises two layers, namely the light-sensitive emulsion layer and the colour producing nuclear layer, but the developer for the colour producing reaction must then be added to the paste. In this variation, which is not an object of this invention, the use of auxiliary developer is superfluous because its function is taken over by the developer in the paste.

The non-diffusible developers which are to be used according to the invention have little or no effect as photographic developers when used along in an alkaline medium. It has been found that in the presence of small quantities of auxiliary developers such as those of the pyrazolidone-3 series, they are extremely active de velopers (see for example US. Pat. No. 3,705,035), Under these conditions, they have at least the same activity as the diffusible developers conventionally used. The auxiliary developer may be incorporated in one of the layers of the light-se nsitive element or added to the activator paste. The non-diffusible developers used according to the invention are added to the casting solutions for the silver halide emulsion layers or the nuclear layers in the form of a dispersion, emulsion or solution, e.g. in water or in organic solvents which are miscible with water such as short chain aliphatic alcohols or dimethylformamide. The concentration of non-diffusible developer in the layer may vary within wide limits. It depends on the efiect required, the nature of the reduc tion process and the nature of the silver halide. Quantities of about 0.1 to 1 mol per mol of silver halide are generally sufficient, these figures being applicable to both the silver halide emulsion layer and the nuclear layer. In the latter case the amount of developer is considered in relation to the amount of silver halide in the associated silver halide emulsion layer. The optimum quantity can easily be determined by a few simple laboratory tests. Concentrations of between 0.2 and 0.5 mol per mol of silver halide are preferred.

The usual well known spectrally sensitizing dyes may be used for spectrally sensitizing the light-sensitive silver halide emulsion layers, for example additional spectral sensitization of the emulsions used for producing the light-sensitive element can be achieved by treating the emulsions with a solution of a sensitizing dye in an organic solvent or by adding a suitable spectrally sensi tizing dye to the emulsion in the form of a dispersion, for example as disclosed in British Patent No. 1,154,781. To achieve optimum sensitizing effects, sensitizing dyes are added to the emulsion at the last stage in the preparation of the emulsion or earlier.

Dyes suitable for spectral sensitization of the emulsions are, for example, the usual monomethine or polymethine dyes such as acid or basic cyanines, hemicyanines, streptocyanines, merocyanines, oxonoles, hemioxonoles and styryl dyes, and trinuclear or multinuclear methine dyes, for example rhodacyanines or neocyanines. Sensitizers of this kind have been described, for example, in the work by F. M. Hamer The Cyanine Dyes and Related Compounds", (1964), In I terscicnce Publishers John Wiley and Sons Combinations of various dyes may also be used for the spectral sensitization of the emulsions. Furthermore, supersensitization can be achieved in known manner by the addition of so-called supersentizing compounds using, as supersensitizing additives, compounds which, for example, do not absorb visible light, e.g. ascorbic acid derivatives, azaindene, cadmium salts and organic sulfonic acids. as described e.g. in US. Pat, Nos. 2,933,390 and 2937089.

If a photographic film unit according to the invention contains several silver halide emulsion layers, these may be arranged in the usual sequence. This means that the blue sensitive silver halide emulsion is the first on the side of the film unit which is exposed to light and is followed by the green sensitive layer which is in turn followed by the red sensitive silver halide emulsion layer. If desired, a layer which contains a yellow dye or a Carey-Lea silver layer may be arranged between the blue and the green sensitive silver halide emulsion layers in order to filter out blue light which may pass through the blue sensitive silver halide emulsion layer. The selectively sensitized silver halide emulsion layers, may, however, also be arranged in a different sequence, for example the blue sensitive layer may be the first on the side exposed to light, followed by the red sensitive layer and lastly the green sensitive layer.

The silver halide emulsions used for preparing the film unit according to the invention may be conventional silver halide emulsions containing silver chloride, silver bromide. silver chlorobromide, silver iodobromide or silver chloroiodobromide or mixtures thereof. Furthermore, the emulsions may be coarse or fine grained emulsions and may be prepared by the usual methods such as those employed, for example, for the preparation of single inflow emulsions and double inflow emulsions. The emulsions may be so-called Lippmann emulsions, ammoniacal emulsions, emulsions which have been ripened in the presence of a thiocya nate or thioether as disclosed, for example, in US. Pat. Nos. 2,222.264; 3,320,069 and 3,271,157.

Lastly, the emulsions may be the so-called regular grain emulsions of the type described by Klein and 12 Moisar in Zeitschrift J, Phot. Sci., Volume 12, No. 5, 1964. pages 242-251.

Furthermore, the emulsions used for preparing the emulsion layers may be sensitized with chemical sensitizers in the usual manner, eg with sensitizing agents which consist of reducing agents; sulfur selenium or tellurium compounds or compounds of gold, platinum and palladium and combinations of the compounds mentioned above. Sensitization may be carried out by the methods disclosed, for example, in US. Pat, Nos. 1,623,499; 2,399,083; 3,297,477 and 3,297,446.

The silver halide emulsion used for preparing the light-sensitive element may also contain compounds which increase sensitivity, e.g. polyalkylene glycols, cationic surface active compounds and thioethers or combinations thereof, the use of which compounds has been disclosed, for example, in US. Pat. Nos. 2,886,437; 3,046,134; 2,944,800 and 3,294,540.

Furthermore, the silver halide emulsions used for preparing the light-sensitive element can be protected against fogging and stabilized against loss of sensitivity in storage. Conventional antifogging agents and stabilizers may be used for this purpose, alone or in combination with each other. Suitable examples include the thiazolium salts disclosed in US. Pat. Nos. 2,131,038 and 2,694,716; the azaindenes disclosed in US. Pat. Nos. 2,886,437 and 2,444,605; the mercury salts disclosed in US. Pat. No. 2,728,663; the urazoles disclosed in US. Pat. No. 3,287,135; the sulfopyrocatechols disclosed in US. Pat. No. 3,236,652; the oximes disclosed in British Patent No. 623,448 as well as nitrone and nitroindazoles', the mercapto tetrazoles disclosed in US. Pat. No. 2,403,927; 3,266,897 and 3,397,987; the polyvalent metal salts disclosed in US. Pat. No. 2,839,405; the thiuronium salts disclosed in U.S. Pat. No. 3,220,839 and the palladium, platinum and gold salts disclosed in US. Pat, No. 2,566,263 and 2,597,9 l 5. The silver halide emulsion layers of the film unit according to the invention preferably consist of gelatine-silver halide emulsion layers in which the silver halide grains have a thickness of from 0.6 to 6 micron,

The non-cliffusible dye-giving compounds are preferably dispersed in a polymeric binder which is permeable to the aqueous alkaline solution, for example gelatine, and they are arranged in a separate layer having a thickness of from 1 to 7 micron. The intermediate lay ers which are permeable to the developing solution, e.g. interlayers made of gelatine, preferably have a thickness of from 1 to 5 micron. The thicknesses of the individual layers may, of course, differ from these figures. Furthermore, other suitable hydrophilic materials may be used for the layers instead of gelatine, e.g. naturally occurring substances such as proteins, cellulose derivatives, polysaccharides such as dextran or gum arabic and polymeric substances, for example polyvinyl compounds which are soluble in water such as polyvinylpyrrolidone or acrylamide polymers.

The photographic emulsion layers and other layers of the photographic monosheet material according to the invention may also contain other synthetic polymers, alone or together with hydrophilic colloids which are permeable to water, for example dispersed polyvinyl compounds, e.g. in the latex form, especially those which are capable of increasing the dimensional stability of the film unit. Typical synthetic polymers which may be used for preparing the layers of monoshcet ma terial according to the invention have been disclosed, for example, in US. Pat. Nos, 3,142,568: 3,193,386;

13 3,062,674; 3,220,844; 3,287,289 and 3,41 1,91 l. The use of water insoluble polymers of alkyl acrylates, alkylmethacrylates, acrylic acid, sulfoalkylacrylates and- /or sulfoalkyl methacrylates has been found to be particularly advantageous. Among these polymers, it is especially advantageous to use those which contain transversely cross-linking points which facilitate hardening and which have recurrent sulfobetaine units as described, for example, in Canadian Patent No. 774,054.

The nuclei for the physical development may consist of conventional development nuclei, e.g. nuclei made of a colloidal metal, such as collodial silver, gold, platinum or palladium or a colloidal metal sulfide or metal sulfide selenide, e.g. colloidal silver sulfide, colloidal nickel sulfide or colloidal zinc sulfide as well as, for example, silver sulfide selenide. Substances which are capable of forming physical development nuclei may also be used, for example reducing agents and compounds which contain a labile sulfur atom.

The silver halide solvent used may consist of any of the known silver halide solvents, e.g. an alkali metal or ammonium thiosulfate or an alkali metal or ammonium thiocyanate, e.g. sodium thiosulfate, ammonium thiosulfate, ammonium thiocyanate or sodium thiocyanate. The silver halide solvent may, if desired, also be accommodated in a separate layer.

Any materials which are capable of mordanting the transferred image dyes or of fixing them in some other manner may be used for preparing the image receiving layers. The most suitable material for producing the image receiving layer in any individual case depends on the dye which is required to be mordanted or fixed. For mordanting acid dyes, the image receiving layer may contain basic mordants, e.g. polymers of aminoguanidine derivatives of vinyl methyl ketone as disclosed, for example, in US. Pat. No. 2,882,156. Other suitable mordants for preparing the image receptor layer are, for example, the 2-vinyl-pyridine polymers and 4-vinylpyridine polymers disclosed in US. Pat. No. 2,484,430 and acetyl tri-methylammonium bromide. Other suitable mordants have been described in U.S. Pat. Nos. 3,271,148 and 3,271,147. The mordanting compounds disclosed in US. Pat. No. 3,271,148 which may be used for producing image receiving layers comprise at least one hydrophilic organic colloid in which are dispersed finely divided droplets of a high boiling organic solvent which is immiscible with water and in which a high concentration of a cationic, nonpolymeric, organic mordant for acid dyes is dissolved. The mordanting compounds disclosed in US. Pat. No. 3,271,147 for producing image receptor layers comprise at least one hydrophilic organic colloid in which particles of a salt of an organic acid with free acid esters and a cationic, non-polymeric organic dye mordant for acid dyes are dispersed in a finely divided form. Suitable cationic or basic mordants for organic dyes are, in particular, quaternary ammonium or phosphonium compounds or ternary sulfonium compounds in which at least one hydrophobic ballast group, e.g. a long chain alkyl or substituted alkyl group is attached to the nitrogen, phosphorus or sulfur atom. Image receiving layers which are also capable of mordanting or fixing the dyes without the aid of special mordants may also be used. An image receiving layer of this kind may comprise, for example, a polymeric layer of N-methoxymethylpolyhexamethylene adipamide which is permeable to the alkaline developing liquid. Other layers of this kind may comprise, for example, a partly hydrolysed polyvinyl 14 acetal or polyvinyl alcohol with or without plasticizers, cellulose acetate, gelatine and/or other similar substances.

It has been found advantageous if the image receiving layer, which is preferably permeable to the alkaline developer liquid, is transparent and has a thickness of from 1 to 10 micron. However, the thickness of this layer is not critical, i.e. it may be above or below these limits, depending on the desired result.

The image receiving layer may contain a compound which absorbs ultraviolet light in order to protect the mordanted dye images against the action of ultraviolet light before they are bleached. Lastly, the image receiving layer may contain an optical brightening agent, e.g. one based on stilbene, coumarine, triazine or oxazole.

If an acid polymer layer which reduces the pH is used in the film unit, the stability of the transferred image is generally increased. It has been found advantageous if the layer which reduces the pH has the effect of reducing the pH of the image layer to less than 10 preferably 5 to 8 and preferably shortly after it has come into operation. The acids used for preparing the layer which reduces the pH may be, for example, the polymeric acids of the kind disclosed in US. Pat. No. 3,362,819. Polymeric acids of this kind reduce the pH of the film unit after development and stop any further transfer of dye and stabilize the dye image. The polymeric acids described consist of polymers which contain acid groups, e.g. carboxylic acid esters and/or sulfonic acid esters which are capable of forming salts with alkali metal ions such as sodium or potassium ions or with organic bases, e.g. with quaternary ammonium bases such as tetramethylammonium hydroxide. The polymers may also contain groups which are capable of yielding acid groups, eg anhyride or lactone groups or other groups which are capable of reacting with bases to form acid groups. It has been found particularly advantageous to use polymeric acids which contain free carboxyl groups and which are insoluble in water in the free acid from and are capable of forming water-soluble sodium and/or potassium salts. Examples of such polymeric acids include the dibasic acid semiester derivatives of cellulose which contain free carboxyl groups, e.g. cellulose acetate hydrogen phthalate; cellulose acetate hydrogen glutarate; cellulose acetate hydrogen succinate; ethylcellulose hydrogen succinate; ethyl cellulose acetate hydrogen succinate; cellulose acetate succinate hydrogen phthalate; ether and ester derivatives of cellulose which have been modified by the action of sulfoanhydrides; e.g. with orthosulfobenzoic acid anhydride, or polystyrene sulfonic acids, carboxymethylcellulose, polyvinyl hydrogen phthalate, polyvinyl acetate hydrogen phthalate, polyacrylic acid, acetals of polyvinyl alcohols with carboxyl substituted or sulfosubstituted aldehydes, e.g. o, mor p-benzaldehyde sulfonic acid or 0-, mor p-benzaldehyde carboxylic acid, partial esters of ethylene/maleic acid anhydride copolymers and the like. Solid monomeric acid compounds may also be used, e.g., palmitic acid, oxalic acid, sebacic acid, hydrocinnamic acid, methanilic acid, p-toluenesulfonic acid and benzene disulfonic acid. Other suitable substances for preparing the layer which reduces the pH have been described, for example, in US. Pat. Nos. 3,422,075, 2,635,048.

The layer which reduces the pH preferably has a thickness of from 8 to 40 micron. Although the layer which reduces the pH is preferably arranged in the image receiving part of the film unit between the support layer and the image receiving layer, it may also be arranged in some other position in the film unit so long as it fulfils the required function. Thus, for example, the pH reducing layer may be arranged in the negative part of the film unit as described, for example, in U.S. Pat. No. 3,362,821, in which case the polymeric acid is encapsulated in a polymeric substance and dispersed in a binder which is permeable to an alkaline solution. In that case, the processing liquid rapidly diffuses through the silver halide emulsion layers. When it has penetrated the polymer capsule of the dispersed particles of polymeric acid, the pH of the film unit drops and the unit is thereby stabilized as a whole. The pH reducing layer may also be arranged on the transparent sheet which is placed on the light-sensitive element of the photographic unit according to the invention.

In addition, an inert retarding layer may advantageously be arranged above the pH reducing layer in order to slow down or control the reduction in pH of the film unit as a function of the velocity with which the alkali diffuses through this inert layer. Retarding layers of this kind may be composed, for example, ofgelatine, polyvinyl alcohol or substances of the kind described, for example, in U.S. Pat. No. 3,459,686. The retarding layer may also serve to equalize the various reaction velocities within a wide temperature range, for example premature reduction in pH may be prevented by operating at temperatures above room temperature, e.g. at temperatues of from 35 to 38C. the retarding layer preferably has a layer thickness of from 2 to micron.

Particularly advantageous results are obtained with retarding layers which are prepared from a hydrolysable polymer or a mixture such polymers which are slowly hydrolysed by the processing liquid. Examples of such hydrolyzable polymers include polyvinyl acetate, polyamides and partially acetalized polyvinyl alcohol. Polyvinyl alcohols and polyvinyl ethers are also suitable.

Photographic layers of the film unit according to the invention may advantageously contain surface active substances such as saponin, anionic compounds such as alkylaryl sulfonates of the kind described e.g. in U.S. Pat. No. 2,600,831, amphoteric compounds, e.g. the compounds disclosed in U.S. Pat. No. 3,133,816, and water-soluble adducts of glyidol and an alkoxyphenol as disclosed, for example, in British Patent No. l,022,878.

If the monosheet material according to the invention contains other light-absorbing substances such as filter dyes or shielding dyes in addition to the dye-giving compounds they must be incorporated in a diffusionfast form in the layers.

The additives used for preparing the silver halide emulsions may be applied from aqueous solutions or solutions with organic solvents. The compounds may be added by various known methods as disclosed, for example, in U.S. Pat. Nos. 2,912,343; 3,342,605, 2,996,287 and 3,425,835.

The usual known coating methods may be used for preparing the light-sensitive element of the photographic film unit according to the invention, e.g. dip coating, coating with an air knife, so-called curtain coating or extrusion coating using a coating funnel e.g. as disclosed in U.S. Pat. No. 2,681,194. If desired, two or more layers may be applied to the support layer simultaneously, for example by the methods described in U.S. Pat. No. 2,761,79l and British Patent No. 837,095.

The usual organic and inorganic hardeners may be used either alone or in combination with each other for hardening the hardenable layers of the photographic film unit according to the invention, for example aldehydes or blocked aldehydes, ketones or carboxylic acid derivatives, sulfonate esters, sulfonyl halides and vinyl sulfonyl ethers, active halogen compounds, epoxy compounds, aziridines, active olefins, isocyanates, carbodiimides, hardeners which contain various hardening groups such as epoxy groups and halogen groups or aldehyde groups, or polymeric hardeners, e.g. oxidized polysaccharides such as dialdehyde starch and oxyguargum.

The alkaline processing liquid may comprise a conventional aqueous solution of an alkaline compound such as sodium hydroxide or sodium carbonate or of an amine such as diethylamine, preferably with a pH above 12, of the kind which has been described for carrying out diffusion transfer processes. The liquid preferably also contains a compound which increases the viscosity, in particular a high molecular weight polymer, e.g. a water-soluble ether which is inert towards alkaline solutions, e.g. hydroxyethylcellulose or an alkali metal salt of carboxymethylcellulose such as sodium carboxymethylcellulose. The concentration of the viscosity increasing compound is preferably from 1 to 5% by weight, based on the weight of processing liquid, so that the viscosity of the processing liquid is preferably from cPs to 200,000 cPs. If desired, an ahesive may be added to the liquid to increase the bond between the transparent sheet and the light-sensitive element after development.

If desired, the alkaline processing liquid may also contain a desensitizing compound, e.g. methylene blue, a heterocyclic compound substituted by at least one nitro group or a 4,4' bipyridinium salt to ensure that the light-sensitive element cannot be further exposed and rendered developable after removal from the camera.

The processing liquid may also contain some clouding agent or substance which makes it opaque, provided that the substance produces only the required cloudiness or impermeability to light. Typical suitable opacifying agents are: Carbon black, barium sulfate, zinc oxide, barium stearate, silver platelets or silver flakes, silicates, aluminium oxide, zirconium oxide, zirconium acetyl acetate, sodium zirconium sulfate, kaolin, feldspar, titanium dioxide, organic dyes such as nigrosines or mixtures of the said substances, provided they produce only the desired degree of impermeability to light or opacity. The clouding agent should be used at such a concentration that it prevents any further exposure of the silver halide emulsion layer or layers of the film unit to room light or daylight entering through the upper transparent sheet after the processing liquid has been distributed between the upper transparent sheet and the layer underneath it.

It has been found, for example, that carbon black or titanium dioxide causes sufficient clouding or impermeablility to light when used at a concentration of from 5 to 40% by weight in the processing liquid. When the liquid and clouding agent have been distributed in the film unit, the development of the exposed film unit may be carried out outside the camera in the presence of actinic radiation, i.e. in daylight or room light, because the processing liquid which contains the clouding agent and the opaque, reflective layer which is permeable to alkaline liquid protect the silver halide emulsion or emulsions of the film unit sufficiently against incident light. If the bands or strips used along the edges to bind the unit together are also opaque, then entry of actinic radiation is also prevented at the edges of the silver halide emulsion layer or layers.

The alkaline-permeable, opaque, light reflective layer of the light-sensitive element of the film unit may also contain any of a very wide variety of clouding agents or opacifying agents dispersed in the binder, provided only that these agents produce the desired properties. Clouding agents which have proved to be particularly advantageous for this layer are those which form white, light-reflecting layers because these produce an aestetically pleasing background for the transferred color image. Suitable clouding agents for these opaque, light reflecting layers are, for example, titan titanium dioxide, barium sulfate, zinc oxide, sulphate, zinc oxide, barium stearate, silver flakes or platelets, silicates, aluminium oxide, zirconium oxide, zirconium acetyl acetate, sodium zirconium sulphate, kaolin, feldspar or mixtures thereof. The clouding agents may be dispersed in conventional binders provided the binders form a layer which is permeable to the alkaline processing liquid. The binder of this layer may advantageously consist of gelatine or polyvinyl alcohol, for example. Optical brightening agents may advantageously be incorporated in the opaque, light reflecting layer, for example those based on stibene, coumarine, triazine and- /or oxazole. if it is desired to increase the clouding capacity or degree of opaqueness of the light-reflecting layer further, dark colored clouding agents may also be incorporated, e.g. carbon black or nigrosine dyes.

Another possible method of increasing the clouding capacity or impermeability to light of the light-reflecting layer comprises arranging underneath it a separate opaque layer which is permeable to the alkaline processing liquid and consists of a binder in which, for example, carbon black or nigrosine dyes are dispersed. The binder of this layer may also consist of gelatine or polyvinyl alcohol, for example.

The opaque light-reflecting layer or layers should preferably have a density of at least 4, preferably more than 7 and be practically impermeable to actinic radiation.

The opaque light-reflecting layer or layers which is or are permeable to an alkaline liquid should preferably have a thickness of from 10 to 100 micron althrough the thicknesses may also lie outside this range, depending on the clouding agent used and the required degree of opacity.

The transparent cover sheet of the film unit may consist of any transparent substance provided that it has no deleterious effect on the photographic properties of the film unit and is dimensionally stable. Typical flexible support layers which are permeable to actinic radiation consist of foils of cellulose nitrate, cellulose acetate, polyvinyl acetals, polystyrene, polyethylene terephthaiate, polycarbonates, poly-a-olefines, such as polyethylene and polypropylene and other polymers as well as glass. The transparent sheet preferably has a thickness of from 50 to 150 micron. It may be provided with a layer of adhesive which is capable of being activated by the processing liquid to increase the bond between the sheet and the light-sensitive element after development.

If the light-sensitive element is not protected against further exposure to light by forcing an opaque processing liquid which contains a clouding agent between the uppermost light-sensitive layer and the transparent cover sheet, the film unit must be covered with a light impermeable foil when it leaves the camera, A foil of this kind may advantageously be fixed to the front edge of the film unit and is folded back or rolled up while inside the camera so as not to prevent exposure of the light sensitive element through the transparent cover sheet and it is only leaving the camera that it is firmly placed or glued to the transparent cover sheet. A covering foil of this kind is preferably pigmented white on the back to form an attractive white back for the finished image. The film unit container which can be split open may be constructed as disclosed, for example, in US Pat. Nos. 2,543,181; 2,634,732; 2,653,732; 2,723,051; 3,056,492; 3,056,491 and 3,152,515. Containers of this kind are generally made of a rectangular sheet of material which is impermeable to liquid and air. This sheet is folded longitudinally to form two walls which are then sealed together along their longitudinal edges and ends to form a cavity containing the proce ssing liquid with clouding or opacifying agent. The seal along the longitudinal edge is weaker than that along the other edges so that the liquid contents of the container can easily escape along this edge when hydraulic pressure is exerted.

The drawing serves to explain the invention in more detail. It shows a section through a monosheet material useful for practicing the invention, It is however to be understood that while reference to a monosheet material is made at various places of the description the process of the invention is not limited to the use of monosheet materials.

The monosheet material shown in the FIGURE is composed of the transparent support 10, the image receiving part 20 which contains the image receiving layer 23 in addition to other auxiliary layers such as acid polymer layer and retarding layer, the light reflecting layer 30, the light sensitive element 40 and the transparent cover sheet 50 which includes a layer 51 containing a silver salt solvent, the coversheet 50 being separated from the uppermost layer of the light sensitive element 40 by spacer strips 55 so that a cavity for receiving a calculated quantity of processing liquid is formed between the uppermost layer, the cover sheet 50 and the spacer strips.

The light-sensitive element 40 consists of nuclear lay ers 41, 44 and 47 which contain different non-difi'usible dye-giving compounds yielding a cyan, magenta or yellow image dye and a non-diffusible color-forming developer, and the light-sensitive silver halide emulsion layers 42 (red sensitive). 45 (green sensitive) and 48 (blue Sensitive) which contain a non-diffusible devel oper. The light-sensitive element 40. also includes the separating layers 43 and 46 which serve to prevent accidental diffusion of dissolved silver halide.

in a multicolor diffusion transfer process according to the invention wherein a monosheet material is used, the unit is first exposed through the transparent sheet 50. It is then developed by passing it through pressure elements which split the container for processing liquid arranged at the side by breaking the seal along the longitudinal edges so that the alkaline liquid with clouding agent can be released from the container and poured between the transparent cover sheet 50 and the uppermost layer 48 of the light sensitive element. The alkaline processing liquid successively penetrates the silver halide emulsion layers 48, 45 and 42 and initiates the development of the latent images contained therein.

That portion of silver halide which has not been developed is dissolved by the silver halide solvent to form a complex and developed by a physical development process in whichever is the adjacent nuclear layer 47, 44 or 41. 1n these nuclear layers diffusible yellow. magenta and cyan dyes are released from the dye-giving compounds. At least part of the diffusing cyan. magenta and yellow dyes which are present in image'vise distribution is then transferred to the image receiving layer 23 in which a positive dye image is produced. This image can then be viewed as non-sidereversed image through the transparent support layer 10, the opaque. reflective layer 30 serving as background.

The following examples serve to explain the invention in more detail. The formulae of compounds L, M, N and O are given in the appendix.

EXAMPLE l The light-sensitive element of a photographic monosheet material according to the invention was first prepared by applying the following layers in the given se quences to a transparent cellulose acetate film support layer (the concentrations given refer to 1 m 1. an image receiving layer of 3.8 g of octadecyltrimethyl ammonium monomethylsulfate and 9.5 g of gelatine;

2. an opaque light reflective layer which is permeable to alkaline processing liquid and consists of 48.5 g of titanium dioxide and 4.85 g of gelatine.

3. a nuclear layer containing 1.32 g of compound L which forms a cyan transfer dye. 4.5 mg of silver sulfide nuclei. 0.1 g of carbon black, 0.88 g of developer 11/8 and 2.5 g of gelatine;

4. a red sensitive silver bromide emulsion layer of 2 g of gelatine, 1.1 g of silver, 0.37 g of developer 1!] and 1.23 g of developer U3;

5. a separating layer of 2.6 g of gelatine, 0.2 mg of sil ver sulfide and 0.12 g of developer U3;

6. a nuclear layer containing 0.48 g of compound M which forms a magenta transfer dye. 3.8 mg of silver sulfide nuclei. 0.76 g of developer 11/8 and 2.1 g of gelatine;

7. a green sensitive gelatine-silver bromide emulsion layer containing 2 g of gelatine, 1.1 g of silver and 1.23 g of developer [/3 and 0.37 g of developer 1/1',

8. a separating layer of 2.6 g of gelatine. 0.2 mg of silver sulphide nuclei and 0.12 g of developer H3;

9. a nuclear layer containing 0.85 g of compound N which forms a yellow transfer image dye, 4.2 mg of silver sulfide, 0.85 g of developer 11/8 and 2.4 g of gelatine;

10. a blue sensitive gelatine silver bromide emulsion of 2 g of gelatine, 1.1 g of silver and 1.23 g of developer 1/3 and 0.37 g of developer 1/1;

1 l. a layer of 1.2 g ofgelatine and 0.12 g of l-phenyL 3pyrazolidone. A transparent cover sheet of cellulose acetate comprising a gelatine layer consisting of 5.7 g of gelatine and 1.14 g of sodium thiosulfate H O) was then placed with its active side on the uppermost layer of light sensitive element. A container designed to be split open to release an alkaline processing liquid of the following composition was used to develop the light sensitive element which had been exposed imagewise:

g of sodium hydroxide.

g of Natrosol HHR 250 (highly viscous hydroxy ethyl cellulose) made up to 1000 ml with water.

tion of the original on a white background became visi ble when viewed through the transparent film support layer.

EXAMPLE 2 Another light-sensitive monosheet material was prepared by applying the following layers in the given sequence to a transparent cellulose acetate film support layer (the figures are based on 1 m 1. Image receiving layer as in Example 1;

2. an opaque light reflecting layer as in Example 1;

3. a nuclear layer containing 1.32 g of compound L which forms a cyan transfer dye, 3.5 mg of silver sulfide selenide nuclei, 0.1 g of carbon black. 2.0 g of devel oper 11/8 and 2.4 g of gelatine;

4. a red sensitive gelatine silver bromide emulsion layer consisting of 2.3 g of gelatine, 1.2 g of silver and 1.35 g of developer 1/9;

5. a layer of 1.25 g of gelatine and 0.06 g of l-phenyl- 3-pyrazolidone.

The material was processed with paste and cover sheet as described in Example 1. A monochrome reproduction of the original was obtained.

EXAMPLE 3 The process described in Example 2 was repeated except that in layer 4 developer [/8 was used instead of developer 1/9. The result obtained corresponded to that described in Example 2.

EXAMPLE 4 A photographic monosheet material compound of the following layers was prepared:

1. an image receiving layer of 3 g of octadecyltrimethyl ammonium monomethylsulfate and 7.5 g of gelatine,

2. an opaque light-reflecting layer of 48.5 g of titanium dioxide and 4.8 g of gelatine;

3. a fogged silver iodobromide emulsion used to intercept developer and consisting of 1.26 g of silver, 0.68 g of gelatine and 0.41 gof l-(4'-phenoxy-3'-sulfophenyl)-3-heptadecylpyrazo1one-5 (compound 0; interceptor for oxidized color-forming developer);

4. a separating layer of 0.89 g of gelatine, 0.27 g of compound 0 and 0.18 g of carbon black;

5. a nuclear layer containing 1.32 g of compound L which forms a cyan transfer dye, 4.5 mg of silver sulfide nuclei and 2.5 g of gelatine;

6. a red sensitive gelatine silver bromide emulsion layer of 2 g of gelatine and 1.1 g of silver and 1.65 g of developer 1/7;

7. a separating layer of 2.35 g of gelatine. 0.29 g of compound 0 and 0.2 mg of silver sulfide 8. a nuclear layer containing 0.43 g of compound M which forms a magenta transfer dye. 5 mg of silver sul fide nuclei and 2.7 g of gelatine;

9. a green sensitive gelatine silver bromide emulsion layer of 2 g of gelatine, 1.1 g of silver and 1.65 g of developer l/7;

l0. a separating layer of 2.35 g of gelatine, 0.29 g of compound and 0.1 mg of silver sulfide;

l l. a nuclear layer of 035 g of compound N which forms a yellow transfer dye, 4.2 mg of silver sulfide and 2.6 g of gelatine;

l2. a blue sensitive gelatine silver bromide emulsion layer of2 g of gelatine and LI g of silver as well as L65 g of developer 1/7;

13. a layer of L?! g of gelatine.

22 ethyl cellulose) made up to lOOO ml with water. A multicolored reproduction on a white background was obtained as in Example 4.

EXAMPLE 6 An exposed monosheet material comprising layers 1 to 4 of Example 2 was developed for minutes, using the cover sheet of Example I and an auxiliary devel- The material was processed as described in Example oper paste of the following composition (hiilkness 0f 1 by distributing the following liquid: the layer of paste 140 #l 5 g of pyrocatechol, 25 g of sodium hydroxide l g of sodium sulfit 25 g of Natrosol (highly viscous hydroxyethylcellug of sodium hydroxide lose) 25 g of Natrosol HHR 250 (highly viscous hydroxyl g of Sodium 'fl ethyl cellulose) made up to 1000 ml with water. between the transparent film support layer on which a The q y of auxiliary developer was Varied as sodium thiosulfate layer has been cast and the upperw" in the m? belowi h able also Shows the most layer of the light sensitive material. A multicolmaximum and minimum densmesored reproduction of the original on a white back- Table ground became visible after 3 minutes at about 20C.

Auxiliary Quantity bl"! mln EXAMPLE 5 developer (g) The material described in Example 4 was processed phen'i-done if 813 using the following paste: 1.5 |.|u 0.32 25 g of N-butyl-N-B-hydroxyethyl-3-methyl-4- 3:8 81;? ammoamlme, 6.0 0.55 0.31 8 g of sodium sulfite, 25 g of sodium hydroxide, 3O 25 g of Natrosol HHR 250 (highly viscous hydroxy- Appendix of formulae to the Examples:

Formula L CH 3 9 NH- CH i i l B 0 NH Q OCH S0 Z Z=-HN-N-C NH OH N fl 2 I l OCH (ca so H B 3 2 3 3 S0 H S0 3 SO -Z 1. A photographic dye diffusion transfer process for the production of positive coloured transfer images, comprising the steps of a. producing a negative silver image by development in a light-sensitive silver halide emulsion layer which has been exposed imagewise,

b. transferring by means of a silver halide solvent the silver halide that remains undeveloped into an associated layer which contains development nuclei and a non-diffusible dye-giving compound developing the transferred silver halide at the de velopment nuclei to form a positive silver image and simultaneously an image distribution of developer oxidation products d. causing a condensation reaction between the developer oxidation products produced in this associated layer and the non-diffusible dye-giving compound to release a diffusible dye therefrom, and

e. transferring the diffusible dye to an image receptor layer to form a dye image therein, wherein the improvement comprises i. the light-sensitive silver halide emulsion layer contains a nondiffusible silver halide developer compound which is incapable of an oxidative condensation reaction with the non-diffusible dye-giving compound,

ii. the associated binder layer which contains development nuclei and the dye-giving compound contains a non-diffusible developer compound which in its oxidized form is capable of undergoing a condensation reaction in the associated layer with the dye-giving compound to release the diffusible preformed dye thereform, and

iii. the development is carried out in the presence of catalytic quantities of a diffusible auxiliary developer.

2. The process as claimed in claim 1, wherein the lightsensitive silver halide emulsion layer and the associated binder layer containing development nuclei and the dye-giving compound form one of three color units in a light-sensitive element.

3. The process as claimed in claim 1, wherein the light-sensitive silver halide emulsion layer, the associ-, ated binder layer containing development nuclei and the dye-giving compound and the image receptor layer are comprised in a photographic monosheet.

4. Process as claimed in claim I, wherein the non-diffusible developer compound in the silver halide emulsion layer is a non-diffusible hydroquinone compound.

5. Process as claimed in claim 4, wherein the non-diffusible developer compound in the silver halide emulsion layer is a non-diffusible hydroquinone compound of the following formula:

- associated with the silver halide emulsion layer and containing development nuclei contains a non-diffusible, dye-giving compound of the following formula:

wherein R denotes hydrogen, an alkyl group containing up to 20 C atoms, an aralkyl group, an aryl group or an amino group which is substituted by alkyl or aryl, and two alkyl groups attached to the nitrogen may be joined together to form a ring,

R denotes an alkyl group containing up to 20 C atoms, an aralkyl group, an aryl group, an acyl group derived from an aliphatic carboxylic acid containing up to 20 C atoms or an aromatic carboxylic acid or an amino group which is substituted by alkyl or aryl, and two alkyl groups attached to the nitrogen may be joined together fo form a ring, or

R and R together denote the ring members required for completing a carbocyclic or heterocyclic group;

at least one of the groups R and R carries the group X denotes a sulfonyl group, a carbonyl group or a single chemical bond;

A denotes photographically inert group which confers diffusion resistance and B denotes a dye group.

7. Process as claimed in claim 1 wherein the diffusible auxiliary developer is selected from the group consisting of p-Methylaminophenol, 2,4-diaminophenol, p-benzylaminphenol, l-phenyl-B-pyrazolidone and reductone, and phenidone.

i t i t 

1. A PHOTOGRAPHIC DYE DIFFUSION PROCESS FOR THE PRODUCTION OF POSITIVE COLOURED TRANSFER IMAGES, COMPRISING THE STEPS OF A. PRODUCING A NEGATIVE SILVER IMAGE BY DEVELOPMENT IN A LIGHT-SENSITIVE SILVER HALIDE EMULSION LAYER WHICH HAS BEEN EXPOSED IMAGEWISE, B. TRANSFERRING BY MEANS OF A SILVER HALIDE SOLVENT THE SILVER HALIDE THAT REMAINS DEVELOPMENT NUCLEI AND A NON-DIFFUSIBLE WHICH CONTAINS DEVELOPMENT NUCLEI AND NON-DIFFUSIBLE DYE-GIVING COMPOUND C. DEVELOPING THE TRANSFERED SILVER HALIDE AT THE DEVELOPMENT NUCLEI TO FORM A POSITIVE SILVER IMAGE AND SIMULTANEOUSLY AN IMAGE DISTRIBUTION OF DEVELOPER OXIDATOON PRODUCTS D. CAUSING A CONDENSATION REACTION BETWEEN THE DEVELOPER OXIDATION PRODUCTS PRODUCED IN THIS ASSOCIATED LAYER AND THE NON-DIFFUSIBLE DYE-GIVING COMPOUND TO RELEASE A DIFFUSIBLE DYE THEREFROM, AND E. TRANSFERRING THE DIFFUSIBLE DYE TO AN IMAGE RECEPTOR LAYER TO FORM A DYE IMAGE THEREIN, WHEREIN THE IMPROVEMENT COMPRISES I. THE LIGHT-SENSITIVE SILVER HALIDE EMULSION LAYER CONTAINS A NONDIFFUSIBLE SILVER HALIDE DEVELOPER COMPOUND WHICH IS INCAPABLE OF AN OXIDATIVE CONDENSATION REACTION WITH THE NON-DIFFUSIBLE DYE-GIVING COMPOUND, II. THE ASSOCIATED BINDER LAYER WHICH CONTAINS DEVELOPMENT NUCLEI AND THE DYE-GIVING COMPOUND CONTAINS A NON-DIFFUSIBLE DEVELOPER COMPOUND WHICH IN ITS OXIDIZED FORM IS CAPABLE OF UNDERGOING A CONDENSATION REACTION IN THE ASSOCIATED LAYER WITH THE DYE-GIVING COMPOUND TO RELEASE THE DIFFUSIBLE PREFORMED DYE THEREFROM, AND III. THE DEVELOPMENT IS CARRIED OUT IN THE PRESENCE OF CATALYTIC QUANTITIES OF A DIFFUSIBLE AUXILIARY DEVELOPER.
 2. The process as claimed in claim 1, wherein the light-sensitive silver halide emulsion layer and the associated binder layer containing development nuclei and the dye-giving compound form one of three color units in a light-sensitive element.
 3. The process as claimed in claim 1, wherein the light-sensitive silver halide emulsion layer, the associated binder layer containing development nuclei and the dye-giving compound and the image receptor layer are comprised in a photographic monosheet.
 4. Process as claimed in claim 1, wherein the non-diffusible developer compound in the silver halide emulsion layer is a non-diffusible hydroquinone compound.
 5. Process as claimed in claim 4, wherein the non-diffusible developer compound in the silver halide emulsion layer is a non-diffusible hydroquinone compound of the following formula:
 6. Process as claimed in claim 1, wherein the binder associated with the silver halide emulsion layer and containing development nuclei contains a non-diffusible, dye-giving compound of the following formula:
 7. Process as claimed in claim 1 wherein the diffusible auxiliary developer is selected from the group consisting of p-Methylaminophenol, 2,4-diaminophenol, p-benzylaminphenol, 1-phenyl-3-pyrazolidone and reductone, and phenidone. 